Sample holder and method for spectrographic analysis



'April 28, 1959 H. TODD 2,884,552

SAMPLE HOLDER AND METHOD FOR SPECTROGRAPHIC ANALYSIS Filed March 16,1955 2 Sheets-Sheet 1 I34 JNVENTOR.

men/4 72200 'H/s ATTORNEY April 28, 1959 H. ODD 2,884,552

SAMPLE HOLDER AND METHOD FOR SPEC TROGRAPHIC ANALYSIS I Filed March 16,1955 2 Sheets-Sheet 2 IN VEN TOR.

WENQV 7000 M5 ATTOQ/VEY improved method of trasted with pin-shapedsamples. holders include a carbon electrode and a means for is used foranalyzing United States Patent SAMPLE HOLDER AND-METHOD FQRSPECTROGRAPHIC ANALYSIS Henry Todd, Monongahela, Pa., assignor to UnitedStates Steel Corporation, acorporation of New Jersey Application March16, 1955, Serial No. 494,686 8 Claims. (Cl. 313-146) This inventionrelates to an improved holder for samples undergoing spectrographicanalysis and to an spectrographic analysis.

'The holder and'methodofmy invention are used with samples which havearelatively 'large fiat surface, con- Conventionally such mounting thesample with its flat surface spaced a standard distance above theelectrode. A high voltage electric current is applied to the sample andelectrode to produce anarc'therebetween. -A suitable spectroscope lightfrom this are to furnish an analysis ofthe sample.

An object of the present invention .is to provide a holder in which theelectrode and sample are relatively movable while the latter undergoesanalysis, whereby the arc emanates 'from various spots on the sample toassure a more representative analysis.

A further object is to provide an improved holder which is adapted toaccommodate samples of either standard or non-standard dimensions whilemoving them relatively to the electrode.

A further object is to provide an improved sample holder in which thesample mounting means carries a spacer for positioning the electrode andis movable manually to align the spacer with the electrode for spacingthe latter, and thereafter is motor driven while the sample actually isbeing analyzed.

A further object is to provide an improved method of spectrographicanalysis in which the spot on the sample where the electric arc emanatescontinually varies to assure a more-representative analysis.

In accomplishing these and other objects of the invention, I haveprovided improved details of structure, a preferred form of which isshown in the accompanying drawings, in which:

Figure 1 is a top plan view of a sample holder constructed in accordancewith my invention;

Figure 2 is a vertical longitudinal section on line IIII of Figure 1;

Figure 3 is a horizontal section on line III-III of Figure' 2;

Figure 4 is a vertical section on line IVIV of Figure 1;

Figure 5 is a fragmentary perspective view of the holder illustrating anoversize sample mounted therein; and

Figure 6 is a view similar'to Figure 4, but showing a larger oversizesample mounted in the holder.

My holder comprises a base 10, a plurality of posts 12 upstanding fromsaid base, and a platform 13 supported on said posts in spaced relationabove the base. The platform is of rigid insulating material, such as asuitable plastic, and preferably is composed of upper and lower sections13a and 13b to facilitate fabrication. A carriage 14 of conductivematerial, preferably hard steel, is mounted on the platform 13 formovement in a longitudinal direction, either manually or by a powerdrive as hereinafter explained.

carriage 14 a standard ice The base'10 carries an electrode support 15towhich a spring clamp 16 is attached. An-upstanding carbon electrode 17is-mounted in the support 15 and held by said clamp. The platform 13contains an elongated slot 18 which receives said electrode with theupper end of the electrode terminating below the underface of thedistance x. The underface of the carriage carries an electrode spacer 19which rides loosely in the slot 18 as the carriage moves. To space theelectrode properly, the carriage is moved manually to a position wherethespacer 19 is directly above the electrode 17 an'd'the latter isshoved manually upwardly until it abuts the spacer and clamped. Tofacilitate thus positioning the carriage, the-upper face of the platform13 preferably has an index marking 20 with which the edge of thecarriage is alignedkwhen the spacer is aligned with the electrode.

The carriagedrive'illustrated includes a screw-threaded shaft 21journaled in a longitudinal recess 22 in the upper face of theplatform13. The shaft 21 is driven from a reversible electric motor 23, frictionwheels 24 and 25, a worm 26, anda worm gear 27 which is keyed to theshaft. A transverse shaft 28 is journaled within the carriage 14 andcarries a worm gear 29 located within a recess 30 in the nnderface ofthe carriage. This latter worm gear-meshes with the threads on the shaft21. A brake 31 is mounted in a vertical bore in he carriage -14 forengagement with the transverse shaft 28 (Figure 4). A set screw 32 isthreadedly engaged with the carriage within this bore and bears againstthe top of the brake 31. Tightening the set screw applies the brake tothe shaft 28, while loosening the set screw releases the brake. When'thebrake is applied, the worm gear 29 is fixed, whereby rotation of thescrew-threaded shaft21 moves the carriage. 'The carriage can be movedmanually by turning the worm 26, since the friction wheels 24 and 25allow relative slippage. The upper face of the platform contains guidegrooves 33 and the carriage has corresponding tongues which ridetherein.

The carriage 14 contains a socket 34 which is longitudinally alignedwith the electrode spacer 19 and is adapted to receive asample S ofstandard dimensions (for example /2 inch in diameter). The underface ofthe sample is flush with the bottom of the carriage and located where itcan be traversed across the electrode 17. After the electrode ispositioned as already described, the carriage 14 is moved back manuallyto a position where one edge of the sample is directly over theelectrode. The motor 23 then is operated in'the appropriate direction totraverse the carriage and sample slowly across the electrode, while thecircuit to the electrode and sample is energized to produce an arctherebetween. Electric connections to the carriage 14 and electrode 17are indicated schematically at 35 and 36 in Figure 2. The edge of theplatform 13 has a recess 37 through which the arc is exposed to aspectroscope (not shown). The platform contains a horizontal duct 38 forexhausting the fumes created by the arc. Preferably the duct has aconnection to a'suitable exhaust fan, not shown.

As shown in Figure :5, the end of the carriage 14 carries a sampleclamping plate 39 for mounting oversize samples S The plate 39 is fixedto rods 40 which are slidably mounted in bores in the carriage.Preferably the bores also contain tension springs 41 which urge the rodsand clamping plate to a retracted position (Figure 1). Theend face ofthe carriage contains a vertical groove 42 which is longitudinallyaligned with the electrode spacer 19. The sample S is clamped betweenthe plate 39 and the end face of the carriage within the groove 42.After an oversize sample is thus mounted, it is analyzed in the samefashion as a standard sample S, except that the starting position of thecarriage for traversing the sample is of course farther to the left. Ifnecessary, adjustments in the starting position can be made .byreleasing the brake 31 from the shaft 28 and manually shoving thecarriage 14 with the gear 29 rolling along the threaded shaft 21.

As shown in Figure 6, still larger samples S can be mounted directly onthe platform 13 outside the clamp plate 39. The carriage can traversesuch samples across the electrode simply by pushing them along theplatform. The carriage 14 carries a pivoted contact arm 43 to establishan electric connection to a sample mounted in this fashion.

According to the method of my invention, the holder is set up bymanually moving the carriage 14 to align the electrode spacer 19 withthe electrode 17 and clamping the electrode with its upper end abuttingthe spacer. The sample is installed on the carriage as shown either inFigure 2, 5 or 6 depending on its dimensions, and the carriage movedmanually to a position where the edge of this sample overlies theelectrode 17. Electric current is applied to the electrode and sample toproduce an arc therebetween, which are is exposed to the spectroscopevia the recess 37. At the same time the motor 23 is operated to drivethe carriage and traverse the sample slowly across the electrode. Sincethe arc emanates from continually varying spots on the sample, a morerepresentative analysis is assured.

While I have shown and described only a single embodiment of myinvention, it is apparent that modifications may arise. Therefore, I donot Wish to be limited to the disclosure set forth but only by the scopeof the appended claims.

I claim:

1. A holder for samples undergoing spectrographic analysis comprising anelectrode, sample mounting means adapted to position a sample in spacedrelation to said electrode, means for applying electric current to theelectrode and sample to produce an arc therebetween, and means fortraversing the sample in a straight line relative to the electrode andthus moving the spot on the sample from Which the arc emanates acrossthe sample at a continually changing distance from the edges thereof.

2. A holder for samples undergoing spectrographic analysis comprising asupport, a carbon electrode mounted on said support, sample mountingmeans carried by said support and adapted to position a sample in spacedrelation to said electrode, means for applying electric current to theelectrode and sample to produce an arc therebetween, and drive means fortraversing the sample in a straight line relative to the electrode andthus moving the spot on the sample from which the arc emanates acrossthe sample at a continually changing distance from the edges thereof.

3. A holder for samples undergoing spectrographic analysis comprising afixed support, a carbon electrode mounted on said support, a movablecarriage mounted on said support, sample mounting means on said carriageadapted to position a sample in spaced relation above said electrode,means for applying electric current to the electrode and sample toproduce an arc therebetween, and drive means for moving said carriage ina straight line for traversing the sample relative to the electrode andthus moving the spot on the sample from which the are emanates acrossthe sample at a continually changing distance from the edges thereof.

4. A holder for samples undergoing spectrographic analysis comprising afixed support, a carbon electrode mounted on said support, a manuallymovable carriage mounted on said support, an electrode spacer on the bottom of said carriage adapted to be positioned over the electrode forregulating the spacing between the electrode and carriage, samplemounting means on said carriage adapted to position a sample in spacedrelation above said electrode, means for applying electric current tothe electrode and sample to produce an arc therebetween, and drive meansformoving said carriage in a straight line for traversing the samplerelative to the electrode and thus moving the spot on the sample fromwhich the arc emanates across the sample at a continually changingdistance from the edges thereof.

5. A holder for samples undergoing spectrographic analysis comprising afixed base, a platform of rigid insulating material supported above saidbase, a carbon electrode mounted on said base, said platform having anopening for said electrode, a carriage movably mounted on said platform,sample mounting means on said carriage adapted to position a sample inspaced relation above said electrode, means for applying electriccurrent to the electrode and sample to produce an arc therebetween, anddrive means for moving said carriage in a straight line for traversingthe sample relative to the electrode and thus moving the spot on thesample from which the arc emanates across the sample at a continuallychanging distance from the edges thereof.

6. A holder as defined in claim 5 including a plurality of samplemounting means on said carriage for accommodating samples of varyingdimensions, said carriage being releasable from said drive means toallow it to be moved manually to position the sample with respect to theelectrode.

7. A holder for samples undergoing spectrographic analysis comprising afixed base, a platform of rigid insulating material supported above saidbase, a carbon electrode mounted on said base and extending upwardlytherefrom, said platform having an elongated opening receiving saidelectrode, a carriage movably mounted on said platform, an electrodespacer on the underface of said carriage and riding in said opening andadapted to be positioned over the electrode for regulating the spacingbetween the electrode and carriage, sample mounting means on saidcarriage adapted to position a sample in spaced relation above saidelectrode, means for applying electric current to the electrode andsample to produce an arc therebetween, and drive means for moving saidcarriage in a straight line for traversing the sample relative to theelectrode and thus moving the spot on the sample from which the arcemanates across the sample at a continually changing distance from theedges thereof, said drive means being releasable from said carriage toallow the latter to be moved manually for positioning the electrodespacer or sample over the electrode.

8. A holder as defined in claim 7 including a plurality of samplemounting means on said carriage for accommodating samples of varyingdimensions.

References Cited in the file of this patent UNITED STATES PATENTS1,979,964 Duifendack et al. Nov. 6, 1934 2,271,893 Brundin et al. Feb.3, 1942 2,324,899 Arthur July 20, 1943 2,344,719 Nusbaum et a1 Mar. 21,1944 2,346,512 Scribner et al. Apr. 11, 1944 2,519,154 Schroeder et al.Aug. 15, 1950 2,731,876 Luechauer Jan. 24, 1956 FOREIGN PATENTS 3,846Great Britain of 1872

